| Abstrakt: |
Medium voltage underground electric cables type 0.6/1 (1,2 kV) Cu/XLPE/DTA/PVC 3x150 mmsq failed in a relatively short time of application. It was found that the XLPE insulator of the cable was not completely cross-linked, as indicated by the presence of a signal assigned to grafted silane (Si-O-CH3 group) in the FTIR spectra of the insulation. The cross-linked density of the insulator was lower than a standard cable, as indicated by its lower gel content. This condition allows water to reside in the material, as shown by the significantly high moisture content of the insulator (0.28%, in contrast to the maximum allowance of 0.015%). The water may enter the system via the damages that may occur from improper handling during the cable installation. Excessive moisture content leads to water tree damage, which continuously grows larger as a result of continuous operation with loads up to 100%. At a certain point, the system could not contain the damage, and thus, total failure of the cable occurred. [ABSTRACT FROM AUTHOR] |
